Method for evaluating fish population resources

Abstract

The present application belongs to the technical field of fishery resource assessment, and provides a method for assessing fish population resource quantity. The method is based on multi-year daily scale fishery data and time corresponding environmental monitoring data, and differentiates the fish capture data and environmental factor data, and on this basis, an environmental response assessment model between fish population resource quantity and various environmental factors is constructed. The assessment model simultaneously reflects the linear influence and nonlinear response characteristics of environmental factors on fish population resource quantity, and the model parameters are determined using historical data, and after the parameters are determined, the fish population resource quantity of the same water area in different time periods can be continuously assessed. The method can effectively improve the stability and accuracy of fish resource quantity assessment, and is suitable for fish resource management and decision support in natural waters such as rivers, lakes and reservoirs.

Description

Technical Field

[0001] This invention relates to the field of fishery resource assessment technology, and more specifically, to a method for assessing fish population resource quantity. Background Technology

[0002] Fish population size is a crucial fundamental parameter for fisheries resource management, catch quota setting, and aquatic ecosystem protection. Scientific assessment of fish population size helps in rationally allocating fishing intensity, determining closed seasons and opening times, and providing early warnings of fish population decline risks. However, in practical applications, accurate assessment of fish population size remains a challenge in fisheries management.

[0003] On the one hand, fish population density is not a static indicator; its changes are influenced not only by the fish's own reproduction, growth, and mortality processes but also by aquatic environmental conditions. Environmental factors such as water temperature, flow velocity, rainfall, river runoff, and dissolved oxygen directly or indirectly affect the activity range, feeding behavior, and spatial distribution of fish, thus significantly impacting their catchability. In natural waters, these environmental factors often change frequently with seasonal and climatic conditions, resulting in distinct temporal fluctuations in fish population density.

[0004] On the other hand, existing methods for assessing fish resources have certain limitations in practical applications. Traditional methods often rely on manual surveys, sample collection, or empirical estimations, which typically require significant manpower and time, and have long survey cycles, making it difficult to reflect dynamic changes in resource levels in a timely manner. While some methods incorporate statistical analysis, they usually only consider the linear effects of environmental factors, making it difficult to describe the nonlinear response characteristics of fish populations to environmental conditions across different ranges. For example, when water temperatures are within a suitable range, fish activity increases and catches rise; conversely, when water temperatures are too high or too low, fish activity is inhibited. Such phenomena are difficult to accurately characterize using a single linear model.

[0005] Furthermore, in actual fisheries production and resource monitoring, daily fish catch data typically exhibit frequent zero values ​​and high numerical dispersion. On the one hand, when fish activity is weak or fishing conditions are unfavorable, there are often several consecutive days without any catch records; on the other hand, when environmental conditions suddenly improve within a short period, the catch may increase dramatically. If raw catch data is used directly for assessment, the assessment results are prone to becoming overly sensitive to individual extreme samples, thus affecting the stability and reliability of the assessment results.

[0006] At the same time, different environmental factors vary greatly in terms of dimensions, value range and distribution patterns. If reasonable data processing is not carried out, it is easy to cause some environmental factors to have excessive weight in the comprehensive evaluation process, thereby masking the actual impact of other environmental factors and causing the evaluation results to deviate from the true ecological situation.

[0007] Therefore, there is an urgent need for a method to assess fish population resources to address these issues. Summary of the Invention

[0008] The purpose of this invention is to solve the technical problems mentioned in the background section and to provide a method for assessing fish population resources, comprising the following steps:

[0009] (1) Obtain daily catch abundance data of fish populations in the target water area for at least six consecutive years, and daily environmental monitoring data that correspond one-to-one with the daily catch abundance data of fish populations on the time scale;

[0010] (2) The daily catch abundance data of the fish population is standardized and transformed to reduce the impact of frequent zero values ​​and extreme catch values ​​on the stability of subsequent evaluation results;

[0011] (3) The daily-scale environmental monitoring data are subjected to logarithmic transformation to reduce the skewed distribution characteristics of the original environmental factor data and enhance the comparability of data between different environmental factors;

[0012] (4) After completing the preprocessing of the fish population data and environmental monitoring data, an environmental response assessment model between fish population resource quantity and multiple environmental factors is constructed based on the processed data.

[0013] The environmental response assessment model simultaneously characterizes the linear response relationship and the nonlinear response relationship reflecting the threshold effect or extreme response characteristics for each environmental factor.

[0014] (5) Using historical multi-year daily fish population data and environmental monitoring data, the parameters of the environmental response assessment model are determined to form a fixed assessment model;

[0015] (6) Input the environmental monitoring data of the time to be evaluated or the evaluation period into the fixed evaluation model, and output the fish population resource quantity evaluation results of the corresponding time or evaluation period.

[0016] As a preferred technical solution of the present invention, the environmental monitoring data includes aquatic environmental factors that affect the activity status, spatial distribution or fishing accessibility of fish populations, and the aquatic environmental factors include at least five of the following: water temperature, flow velocity, rainfall, river runoff and dissolved oxygen.

[0017] As a preferred technical solution of the present invention, the time span of the daily catch abundance data of fish populations and the daily environmental monitoring data used to construct the environmental response assessment model is not less than six years, and the number of data records used to determine the model parameters is not less than 12.

[0018] As a preferred technical solution of the present invention, the standardization conversion process in step (2) adopts a conversion method suitable for discrete counting data, which is used to reduce the interference of zero values ​​and outliers in fish population fishing data on the model construction process.

[0019] As a preferred technical solution of the present invention, the logarithmic transformation process in step (3) adopts the method of taking the logarithm after numerical offset based on the original environmental factor data, so as to avoid the influence of zero values ​​in the environmental factor data on the transformation result.

[0020] As a preferred technical solution of the present invention, the environmental response assessment model combines linear and nonlinear response relationships of each environmental factor to reflect the comprehensive effect mechanism of environmental factor changes on fish population resources.

[0021] As a preferred technical solution of the present invention, the model parameters are determined based on historical multi-year daily fish population data and environmental monitoring data, and are completed through numerical optimization or regression analysis.

[0022] As a preferred technical solution of the present invention, after the fixed evaluation model is formed, without re-determining the parameters, the fixed evaluation model is used for continuous evaluation of fish population resources in the same water area at different time periods.

[0023] As a preferred technical solution of the present invention, the method is applicable to the assessment of wild fish population resources in natural waters such as rivers, lakes, and reservoirs.

[0024] Compared with existing technologies, this invention comprehensively assesses fish population resources by incorporating multi-year daily fish catch data and concurrent environmental monitoring data. This effectively overcomes the problems of long cycles and poor real-time performance inherent in traditional methods relying on manual surveys or single statistical methods. By uniformly modeling historical data and determining the model parameters, continuous assessment of fish population resources at different time periods under the same water conditions can be conducted. This provides fisheries management departments with more timely and stable quantitative reference data, improving the scientific nature and response efficiency of fish resource management decisions.

[0025] In constructing the assessment model, this invention considers both the linear impact of environmental factors on fish population resources and the nonlinear response characteristics that may occur in different environmental ranges. This allows the assessment results to more realistically reflect the actual response patterns of fish populations to environmental changes. Compared to existing technologies that only consider linear relationships, this invention can effectively describe the differentiated impacts of environmental factors such as water temperature and flow velocity on fish activity and catchability under suitable and extreme conditions, thereby improving the accuracy and ecological rationality of fish population resource assessment.

[0026] Furthermore, this invention addresses the practical problems of frequent zero values, high dispersion, and large dimensional differences in daily fish catch data, as well as environmental factors. By performing adaptive data processing on catch data and environmental data separately, it effectively reduces the interference of extreme values ​​and scale differences on the assessment results, enhancing the stability and reusability of the model. This method does not rely on complex field survey equipment or high-cost monitoring methods, and can make full use of existing fishing records and routine environmental monitoring data. It has strong engineering feasibility and application value, and is suitable for assessing fish population resources in various natural water bodies such as rivers, lakes, and reservoirs. Attached Figure Description

[0027] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with embodiments and appendices. Figure 1 The present invention will be further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0029] Example 1: This example uses a natural waterway in the middle and lower reaches of a river in South China as the application object. The hydrological conditions of this waterway are significantly affected by seasonal rainfall, and the fish population fluctuates greatly between different years and seasons. When formulating annual fishing plans and fishing ban management measures, the local fisheries management department urgently needs a method that can combine historical data and real-time environmental conditions to assess the fish population.

[0030] In this embodiment, the mud carp, which has a wide distribution in the water area and is relatively sensitive to environmental changes, was selected as the target fish species. The management department continuously collected daily catch abundance data for mud carp in this water area from 2016 to 2023. This catch abundance data originated from net-catching records and sampling surveys at fixed monitoring points, and can relatively accurately reflect the catchability of mud carp on different days. Simultaneously, daily environmental monitoring data corresponding to each fishing date was collected. This environmental monitoring data included the average water temperature, average flow velocity, daily rainfall, river cross-sectional runoff, and dissolved oxygen content for that day.

[0031] During data processing, it was found that the daily catch abundance data for mud carp exhibited significant dispersion: consecutive days with zero catches occurred, while on certain days with suitable environmental conditions, the catch showed a clear peak. Directly using the raw catch data for evaluation could easily lead to the assessment results being significantly affected by extreme values. Therefore, in the implementation process, historical catch abundance data was first standardized to mitigate the impact of frequent zero-value occurrences and extreme catch records on the stability of subsequent evaluation results.

[0032] After the captured data is processed, the environmental monitoring data undergoes a uniform logarithmic transformation. This process effectively reduces the differences in numerical scale and distribution patterns of various environmental factors, making multiple environmental factors such as water temperature, flow velocity, rainfall, runoff, and dissolved oxygen more comparable in the same assessment model. This prevents a single environmental factor from dominating the assessment results due to excessively large dimensions or numerical ranges.

[0033] Based on the aforementioned data preprocessing, an environmental response assessment model was constructed using diurnal data from multiple historical years to assess the relationship between fish population resources and various environmental factors. This model was designed to consider both the linear impact of environmental factors on fish population resources and the potential nonlinear modulation effects within specific ranges. For example, when water temperature is within a suitable range, mud carp activity increases and catchability improves; conversely, when water temperature is too high or too low, mud carp activity is inhibited, and catches decrease. By simultaneously characterizing both types of effects in the model, the assessment results are made more consistent with actual ecological patterns.

[0034] Subsequently, using historical data from 2016 to 2023, the parameters of the assessment model were determined, forming a fixed assessment model suitable for the conditions of this water area. The model parameters remain stable over a certain period, reflecting the overall response characteristics of the mud carp population to environmental changes. Once the parameters are determined, under the same water conditions, it is unnecessary to rebuild the model or recalculate the parameters for each assessment, thereby improving assessment efficiency.

[0035] In practical application, when entering a new annual fishing management decision-making cycle, the management department obtains environmental monitoring data for several consecutive days before the end of the fishing ban period or the planned opening of the fishing season. After processing the environmental data using the same data processing method as in historical periods, the processing results are input into the aforementioned fixed assessment model to obtain the assessment results of the mud carp population resource quantity for the corresponding date.

[0036] By comprehensively analyzing the assessment results over several consecutive days, management departments can determine whether the current mud carp population is in a recovery phase, a relatively stable phase, or a phase with a high risk of fluctuation. For example, when the assessment results remain at a high level for several consecutive days, it can serve as a reference for appropriately relaxing fishing intensity; when the assessment results show a significant downward trend, management measures such as extending the fishing ban period or restricting fishing intensity can be taken in advance.

[0037] As can be seen from this embodiment, this method can make full use of existing years of fishing records and environmental monitoring data to conduct continuous and reusable assessments of fish population resources without relying on large-scale artificial resource surveys. It takes into account both the stability of the assessment results and has good practical operability, making it suitable for promotion and application in various natural water bodies such as rivers, lakes, and reservoirs.

[0038] Example 2: The technical solution of the present invention will be further described below with reference to a specific embodiment. This embodiment takes a mud carp population in a certain natural water area as the research object. By comprehensively analyzing multi-year daily catch data and concurrent environmental monitoring data, the fish population resource quantity is assessed. It should be noted that this implementation method is not limited to specific fish species or specific water conditions. Without changing the overall technical concept, it is also applicable to other fish populations and different types of natural water areas such as rivers, lakes, and reservoirs.

[0039] In the specific implementation process, the first step is to systematically collect basic data on the target water area. This data includes daily catch abundance data of fish populations over several consecutive years, as well as daily environmental monitoring data that corresponds one-to-one with the stated fishing dates on a time scale. Daily catch abundance data of fish populations reflects the catchability of fish populations under different time conditions, while environmental monitoring data describes the external ecological environment conditions in which fish activity and distribution occur. The environmental monitoring data should include at least five environmental factors that significantly influence fish activity, spatial distribution, or catch accessibility, such as water temperature, current velocity, rainfall, river runoff, and dissolved oxygen.

[0040] Let the first The abundance of native fish caught that day was , No. Heavenly The original monitoring values ​​of each environmental factor ,in , , This represents the total number of historical samples used for modeling and parameter determination.

[0041] After completing the raw data collection, the fish catch abundance data needs to be preprocessed. This is because in actual fisheries production and resource monitoring, daily fish catch data often exhibits frequent zero values ​​and large numerical ranges. If this type of data is directly used for model building, the model parameters are easily dominated by extreme samples, thus affecting the stability and reliability of the evaluation results. Based on the above considerations, this embodiment uses Hellinger transformation to standardize the fish catch abundance data. Specifically, the sum of catch abundance within the historical sample time period is first calculated:

[0042]

[0043] in, This represents the cumulative daily fish catch abundance within the selected historical time window. Indicates the first The original capture abundance of the day.

[0044] Based on this, a Hellinger transformation is performed on each capture record to obtain the standardized capture response:

[0045]

[0046] in, Indicates the first The fish population capture response value after standardization is a dimensionless indicator used to reflect the relative resource level of the fish population at that moment. This standardization effectively reduces the impact of extreme catch values ​​and numerous zero-catch records on the subsequent model building process, providing a reliable foundation for a stable characterization of environmental response relationships.

[0047] After standardizing the captured data, the environmental monitoring data undergoes further preprocessing. Because different environmental factors differ significantly in dimensions, numerical ranges, and distribution patterns, directly incorporating them into the model calculations can easily lead to some environmental factors having excessively high weights, thus masking the true impact of other environmental factors. Therefore, it is necessary to perform a unified transformation on the environmental monitoring data. This embodiment uses a logarithmic transformation to process the environmental factor data, the specific form of which is as follows:

[0048]

[0049] in, Indicates the first Heavenly The values ​​of environmental factors after logarithmic transformation These are the corresponding original environmental monitoring values. Represents the natural logarithm function. This is a numerical offset term used to avoid the problem that logarithmic operations cannot be performed when the original environmental factor value is zero. This transformation effectively reduces the skewed distribution characteristics of the original environmental factor data and enhances the comparability between different environmental factors.

[0050] After preprocessing fish capture data and environmental monitoring data, an environmental response assessment model was constructed based on the processed data, relating fish population size to environmental factors. The model's design aims to simultaneously characterize the linear impact of environmental factors on fish population size and potential nonlinear modulation effects within the same model framework, thereby more realistically reflecting the response characteristics of fish to environmental changes. For the first... In terms of the sky, the model form is defined as:

[0051]

[0052] in, The model represents the first The assessment value given for the population resource of fish species in the sky, This is the intercept term, used to represent the resource quantity level under baseline environmental conditions; For the first The linear response coefficient of an environmental factor is used to describe the degree of linear impact of changes in that environmental factor on fish population resources. For the first The quadratic nonlinear response coefficients of each environmental factor are used to reflect the threshold effect or extreme response characteristics that may occur during the change of environmental factors. For the first Heavenly Logarithmic transformation values ​​of environmental factors.

[0053] To ensure that the model output accurately reflects the standardized capture response characteristics, the aforementioned method is used. As the model fitting target, the model parameters are determined using historical data from multiple years. Therefore, the first... The fitting residual for days is

[0054]

[0055] in, This indicates the deviation between the model's estimated value and the actual captured response.

[0056] Furthermore, using the minimum sum of squared residuals as the optimization objective for solving the problem, the following objective function is constructed:

[0057]

[0058] in, Let be the vector of model parameters to be solved. By optimizing the above objective function, a set of parameter combinations can be obtained that minimizes the overall deviation between the model's prediction results and the historical captured response.

[0059] To facilitate model engineering implementation and subsequent reuse, the above model is further written in matrix form for the first... Celestial structural environment feature vector:

[0060]

[0061] in, The first constant of the environmental feature vector on day i corresponds to the intercept, and the second component corresponds to each factor in a linear or nonlinear manner.

[0062] The design rectangular matrix is ​​obtained by stacking all the historical samples: At the same time, it creates a sound image: For n = 1, 2, 3...i, the expression modulus in a matrix can be expressed as: ,in, This represents the response vector predicted by the model, where each component corresponds to the evaluation result at different time points. This is the vector of model parameters to be solved.

[0063] The parameter vector is solved using the least squares method, and its analytical form is as follows:

[0064]

[0065] in, Indicates matrix transpose. This represents matrix inversion. When a matrix is ​​not invertible or numerically unstable, a generalized inverse or equivalent numerical optimization method can be used to solve it, without affecting the model structure and overall evaluation concept.

[0066] After solving for the above parameters, a stable set of model parameters can be obtained, thus forming a fixed fish population resource assessment model. Once the model parameters are determined, this model can be directly reused for subsequent resource assessments under the same water conditions without the need for repeated parameter estimation.

[0067] In the actual assessment phase, after obtaining environmental monitoring data for a specific assessment time or assessment period, the environmental data is first subjected to a logarithmic transformation consistent with historical periods. Let the assessment date be... The original monitoring values ​​of each environmental factor The corresponding transformation result is:

[0068]

[0069] Based on this, construct the environmental feature vector for the day to be evaluated:

[0070]

[0071] By inputting this feature vector into a fixed evaluation model, the fish population resource quantity assessment result at the time to be evaluated is obtained:

[0072]

[0073] in, This indicates the assessed value of the fish population resource quantity at the time to be evaluated.

[0074] If it is necessary to analyze an assessment period consisting of multiple consecutive time points, the environmental feature vectors of each time point can be arranged into an assessment matrix by row, and multiplied with the parameter vector to obtain the continuous assessment results of fish population resources within the assessment period.

[0075] Example 3: Step 1: Organize the historical capture abundance data and environmental monitoring data of the shad population over 6 years, as shown in Table 1.

[0076] Table 1. Historical fishing data and environmental factors for mud carp populations.

[0077]

[0078]

[0079] Step 2: Perform Hellinger transformation on the scad population data and logarithmic transformation on the environmental factor data. e (y+1) transformation yields standardized data table 2.

[0080] Table 2. Standardized data on historical catch data and environmental factors of mud carp populations.

[0081]

[0082]

[0083]

[0084] Step 3: Input the standardized environmental monitoring data and mud carp population fishing data into the model.

[0085] By inputting this feature vector into a fixed evaluation model, the fish population resource quantity assessment result at the time to be evaluated is obtained:

[0086]

[0087] in, This indicates the assessed value of the fish population resource quantity at the time to be evaluated.

[0088] Furthermore, once a certain amount of environmental monitoring data is obtained, the catchable resources of fish populations can be inferred.

[0089] Through the above implementation methods, a fish population resource assessment method has been formed based on multi-year daily-scale fishing data and environmental monitoring data, combined with differentiated data transformation, linear and nonlinear coupled modeling, parameter determination and fixed model reuse. This method can stably reflect the comprehensive impact of environmental changes on fish population resources while ensuring model interpretability, and has good engineering feasibility and promotion and application value.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for assessing fish population resource quantity, characterized in that, Includes the following steps: (1) Obtain daily catch abundance data of fish populations in the target water area for at least six consecutive years, and daily environmental monitoring data that correspond one-to-one with the daily catch abundance data of fish populations on the time scale; (2) The daily catch abundance data of the fish population is standardized and transformed to reduce the impact of frequent zero values ​​and extreme catch values ​​on the stability of subsequent evaluation results; (3) The daily-scale environmental monitoring data are subjected to logarithmic transformation to reduce the skewed distribution characteristics of the original environmental factor data and enhance the comparability of data between different environmental factors; (4) After completing the preprocessing of the fish population data and environmental monitoring data, an environmental response assessment model between fish population resources and multiple environmental factors is constructed based on the processed data. The environmental response assessment model simultaneously characterizes the linear response relationship and the nonlinear response relationship reflecting the threshold effect or extreme value response characteristics for each environmental factor. (5) Using historical multi-year daily fish population data and environmental monitoring data, the parameters of the environmental response assessment model are determined to form a fixed assessment model; (6) Input the environmental monitoring data of the time to be evaluated or the evaluation period into the fixed evaluation model, and output the fish population resource quantity evaluation results of the corresponding time or evaluation period.

2. The method for assessing fish population resources according to claim 1, characterized in that: The environmental monitoring data includes aquatic environmental factors that affect the activity status, spatial distribution, or fishing accessibility of fish populations. These aquatic environmental factors include at least five of the following: water temperature, flow velocity, rainfall, river runoff, and dissolved oxygen.

3. The method for assessing fish population resources according to claim 1, characterized in that: The time span of the daily catch abundance data of fish populations and the daily-scale environmental monitoring data used to construct the environmental response assessment model shall be no less than six years, and the number of data records used to determine the model parameters shall be no less than 12.

4. The method for assessing fish population resources according to claim 1, characterized in that: The standardization transformation process in step (2) adopts a transformation method suitable for discrete count data to reduce the interference of zero values ​​and outliers in fish population fishing data on the model building process.

5. The method for assessing fish population resources according to claim 1, characterized in that: The logarithmic transformation process in step (3) adopts the method of taking the logarithm after numerical offset based on the original environmental factor data, so as to avoid the influence of zero values ​​in the environmental factor data on the transformation result.

6. The method for assessing fish population resources according to claim 1, characterized in that: The environmental response assessment model combines linear and nonlinear response relationships for each environmental factor to reflect the comprehensive effect of environmental factor changes on fish population resources.

7. The method for assessing fish population resources according to claim 1, characterized in that: The model parameters were determined based on historical multi-year daily fish population data and environmental monitoring data, and were completed through numerical optimization or regression analysis.

8. The method for assessing fish population resources according to claim 1, characterized in that: Once the fixed assessment model is formed, without re-determining the parameters, the fixed assessment model is used for continuous assessment of fish population resources in the same water area at different time periods.

9. The method for assessing fish population resources according to claim 1, characterized in that: The method is applicable to the assessment of wild fish populations in natural water bodies such as rivers, lakes, and reservoirs.

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